Initial-on scr device for on-chip esd protection

A method of providing electrostatic discharge (ESD) protection, comprising:

• providing a silicon controlled rectifier (SCR) including a semiconductor substrate and a well formed in the substrate;
• providing a p-type metal-oxide-semiconductor (PMOS) transistor formed in the well of the SCR including a gate, a first diffused region and a second diffused region spaced apart from the first diffused region;
• providing an n-type region formed in the well being electrically connected to the first diffused region of the PMOS transistor;
• providing a p-type region formed in the substrate being electrically connected to the second diffused region of the PMOS transistor;
• and
• keeping the PMOS transistor at an on state before an ESD event occurs.

A method of providing electrostatic discharge (ESD) protection, comprising:

• providing a silicon controlled rectifier (SCR) including a semiconductor substrate, a well formed in the substrate, an anode formed in the well, and a cathode;
• providing a p-type metal-oxide-semiconductor (PMOS) transistor formed in the well of the SCR including a gate, a first diffused region and a second diffused region spaced apart from the first diffused region;
• providing an n-type region formed in the well being electrically connected to the first diffused region of the PMOS transistor;
• providing a p-type region formed in the substrate being electrically connected to the second diffused region of the PMOS transistor;
• keeping the PMOS transistor at an on state before an ESD event occurs;
• triggering a first current in the well flowing through the n-type region in response to an ESD event;
• triggering a second current in the substrate flowing through the p-type region in response to the first current;
• and
• discharging an ESD current due to the ESD event from the anode to the cathode.